The Flash Hider-QD is designed to mitigate flash when unsuppressed.
Flash Hider-QD 762 is compatible with HX-QD 762, 762 Ti and Magnum Ti suppressors.

Flash Hider-QD 556 is compatible with HX-QD 556k, 556, 762, 762 Ti and Magnum Ti suppressors.
 
762 – Muzzle device length is 2.3 and length added to barrel is 1.7 inches.
556 Regular – Muzzle device length is 2.3 inches, and length added to barrel is 1.7 inches.*
556 Long – Muzzle device length is 2.7 inches, and length added to barrel is 2.1 inches.*
556 XL 13.7″ Muzzle Device Length is 2.9″ and adds 2.3″ to barrel for 13.7″ barreled guns.
*on barrels with 0.6 inch threads.
 
NOTE: Larger caliber mounts are NOT compatible with smaller caliber suppressors. Smaller caliber mounts ARE compatible with larger caliber suppressors.
 
*In an attempt to minimize waste, some suppressors, accessories and muzzle devices may arrive in OSS packaging while we transition to the new HUXWRX packaging.